Riser and manifold gaskets

[Amaier41]

Hello,
I bought a 1980 wellcraft nova 220xl....
My question is...why on a 1980 mercruiser 260 do the riser to manifold gaskets have two soft gaskets with the holes for water to flow through... but have a metal gasket sandwiched between them without the holes ...has an 1/8 inch round hole in metal gasket that is all ? after running engine for 20 min engine won't run open throttle..wants to stall...sometimes will turn over and restart...sometimes won't turn over at all...like there's a load on the starter...risers are hot enough to not be able to touch but for a second.....yet thermostat reads 160deg. Risers are at the rear of engine..
Engine will idle and putt around lake all day long but after (wot) for short period (15) min...it starts like jittering...like to much, or not enough fuel...overheating ? have to back off almost all throttle and limp it back to shore...

Thermostat hasn't gone over 160...had a 160deg. thermostat in it when I checked it & I'm going to put 142deg back in...exhaust manifolds seem good shape. Can see through them with end caps off...how do you know when needed to change em ? They seem good shape... 500 hrs on engine... the water seemed like normal lake water when removed risers and manifolds...minimal brown rusty water when separated risers from manifolds...
Can I leave out metal gasket all together or make the (seep) hole bigger as someone mentioned in another post...risers should be warm but not hot I believe from these other posts?.
There's no evidence of water on oil dipstick but mayonnaise substance under valve covers...on valve cover caps...like tiny puddles on heads...maybe condensation ?
New impeller was installed just before boat purchase

 

[alldodge]

Re: Riser and manifold gaskets

Hello,
I bought a 1980 wellcraft nova 220xl....
My question is...why on a 1980 mercruiser 260 do the riser to manifold gaskets have two soft gaskets with the holes for water to flow through... but have a metal gasket sandwiched between them without the holes ...has an 1/8 inch round hole in metal gasket that is all ? after running engine for 20 min engine won't run open throttle..wants to stall...sometimes will turn over and restart...sometimes won't turn over at all...like there's a load on the starter...risers are hot enough to not be able to touch but for a second.....yet thermostat reads 160deg. Risers are at the rear of engine..
Engine will idle and putt around lake all day long but after (wot) for short period (15) min...it starts like jittering...like to much, or not enough fuel...overheating ? have to back off almost all throttle and limp it back to shore...

Thermostat hasn't gone over 160...had a 160deg. thermostat in it when I checked it & I'm going to put 142deg back in...exhaust manifolds seem good shape. Can see through them with end caps off...how do you know when needed to change em ? They seem good shape... 500 hrs on engine... the water seemed like normal lake water when removed risers and manifolds...minimal brown rusty water when separated risers from manifolds...
Can I leave out metal gasket all together or make the (seep) hole bigger as someone mentioned in another post...risers should be warm but not hot I believe from these other posts?.
There's no evidence of water on oil dipstick but mayonnaise substance under valve covers...on valve cover caps...like tiny puddles on heads...maybe condensation ?
New impeller was installed just before boat purchase

:welcome: to iboats

Sure could use your engine serail number, which will help us identify exactly what your setup is.

The gaskets are designed to keep water from directly floowing water from manifold to the risers to ensure the manifolds stay full of water. There are probably (serial number helps here) hoses running to the risers from the thermostat housing or manifolds to risers.

Sounds like something is getting hot and sizing up with the starter unable to turn over the engine. So long as the boat has been in fresh water the exhaust will last a lot longer, but visual inspections help telling when. If you start developing leaks or water in oil then your probably ok. Without the S/N I'll guess you have a carberated engine and should probably have a 140 degree thermostat. Are there any ports on the engine which have been closed off with caps?

Milky substance under valve covers and valve caps needs to tbe looked into. May want to pull valve covers for a closer look but need more info on your issues.

 

[Amaier41]

Re: Riser and manifold gaskets

Wondering since thermostat was 160 & not 142 if that's going to cause it to run so hot engine will shut down & not want to run... carb is a 4barrel quadrajet...I will get serial number of engine...no ports closed off with caps...was told some milky substance is normal under valve covers..not sure how much is normal

:welcome: to iboats

Sure could use your engine serail number, which will help us identify exactly what your setup is.

The gaskets are designed to keep water from directly floowing water from manifold to the risers to ensure the manifolds stay full of water. There are probably (serial number helps here) hoses running to the risers from the thermostat housing or manifolds to risers.

Sounds like something is getting hot and sizing up with the starter unable to turn over the engine. So long as the boat has been in fresh water the exhaust will last a lot longer, but visual inspections help telling when. If you start developing leaks or water in oil then your probably ok. Without the S/N I'll guess you have a carberated engine and should probably have a 140 degree thermostat. Are there any ports on the engine which have been closed off with caps?

Milky substance under valve covers and valve caps needs to tbe looked into. May want to pull valve covers for a closer look but need more info on your issues.

 

[Bt Doctur]

Re: Riser and manifold gaskets

seems strange to have a 1980 with log manifolds. but if you do there are hoses on the front and rear on the manifolds and hoses going to the risers.
the therm housing has a lot to do with proper cooling.

 

[Amaier41]

Re: Riser and manifold gaskets

You are correct about hoses...risers and manifolds get to hot to keep hand on them or more than a second...they seem clear of sediment though...going to send them out and check for cracks...thought I found heating problem when I saw restrictive gasket covering all the holes except has 1/8 in hole in metal gasket...after reading forums the gaskets seem correct...wondering if making hole little bigger or even adding couple holes would help ?

seems strange to have a 1980 with log manifolds. but if you do there are hoses on the front and rear on the manifolds and hoses going to the risers.
the therm housing has a lot to do with proper cooling.

 

[alldodge]

Re: Riser and manifold gaskets

You are correct about hoses...risers and manifolds get to hot to keep hand on them or more than a second...they seem clear of sediment though...going to send them out and check for cracks...thought I found heating problem when I saw restrictive gasket covering all the holes except has 1/8 in hole in metal gasket...after reading forums the gaskets seem correct...wondering if making hole little bigger or even adding couple holes would help ?

I wouldn't do that, the system was design to work without problems. It worked correctly over 30 years and now has an issue, we just need to find out what the issue is.

 

[Amaier41]

Re: Riser and manifold gaskets

could a water pump be bad even if doesnt make a noise or seep water ? am thinking run without a thermostat temporarily to see if it still gets hot...if it dont than put 142 stat in it...had a 160...and see what we find if anything when check for cracks in manifolds and risers first while they are off

 

[Amaier41]

Re: Riser and manifold gaskets

I found bit of rust in risers and exhaust manifolds...going to tank and have em blasted to see how clean we can get em...definitely a reason they were running hot...rust was clogging the ports

 

[alldodge]

Re: Riser and manifold gaskets

I found bit of rust in risers and exhaust manifolds...going to tank and have em blasted to see how clean we can get em...definitely a reason they were running hot...rust was clogging the ports

Looks like you found the heat problem, not sure if blasting is a good thing, make sure they don't get to thin

 

[Volphin]

Re: Riser and manifold gaskets

Amaier41 you will be wasting your $$. Get a new set of manifolds and risers. The ones you have are WAY past their lifespan if original to the boat.

 

[Amaier41]

Re: Riser and manifold gaskets

Ok Think I'm going to go with center riser conversion by Sierra...seems like a complete kit
Part # 47-19871

 

[Amaier41]

Re: Riser and manifold gaskets

Serial number is 5538913

 

[Amaier41]

Block off plate question

Block off plate question

I have a question about my 1980 mercruiser 260 engine...serial number 553893
raw water cooling doesn't require a block off plate between exhaust manifold and risers...
Closed cooling system does use block off plate and is cooled by antifreeze..
My fwc exhaust manifolds and risers had a block off plate w/an 1/8 inch hole in it sandwiched between 2 soft gaskets...why is that ? System looks original like never touched....rust was clogging the water ports so am replacing with Barr center rise conversion...so another question is do I need a block off plate for manifold to riser with this conversion ?

 

[Bt Doctur]

Re: Block off plate question

Re: Block off plate question

no ,you need an updated thermostst housing going to center rise.

 

[alldodge]

Re: Riser and manifold gaskets

With the kit you have listed will convert your system to newer version. It does change out the thermostat housing which would be needed. Looks like the best way to go but will take a bit of coin.

MANIFOLD CONVERSION KIT (#47-19871)-Performance Product Technologies

 

[Amaier41]

Re: Riser and manifold gaskets

Bought the Barr conversion center rise kit...it DOESNT come with thermostat housing...is original ok or does it need updated ? They say original is fine

 

[alldodge]

Re: Riser and manifold gaskets

Bought the Barr conversion center rise kit...it DOESNT come with thermostat housing...is original ok or does it need updated ? They say original is fine

I'm not sure about that, maybe BTdoc will come in. But.... your number listed the Sierra part number. The flow out of the stat will be different and I'm not sure it will work without, but as before the expert seems to be BTdoctor

 

[Bondo]

Re: Riser and manifold gaskets

Amaier41,.... please stop postin' multiple threads about the same issue,...

'n please stop postin' yer questions in antique threads,...
The Big Red banner is there for a reason,...

 

[Amaier41]

Re: Riser and manifold gaskets

Sorry. Just tryin to fix this issue quickly as possible

 

[Bt Doctur]

Re: Riser and manifold gaskets

center rise use either 2 hoses from the therm housing to the bottom of the manifolds or those 2 hoses plus 2 more that go to the risers.
All depends on the therm housing. Yours sounds like 6 hoses,one for each end of the log manifold and 1 for the riser x2